Machine tool organization and control mechanism



Dec. 11, 1951 w, ANDREW Er 2,577,943

MACHINE TOOL ORGANIZATION AND CONTROL MECHANISM Filed Jan. 10, 1945 3 Sheets-Sheet l INVENTORS MAL/AM K. AND/25W PIC/{A20 fl F020 foMaA/a m .105T

ATTORNEY Dec. 11, 1951 w. K. ANDREW ETAL 2,577,943

MACHINE TOOL ORGANIZATION AND CONTROL MECHANISM 5 Sheets-Sheet 2 Filed Jan. 10, 1945 MACHINE TOOL ORGANIZATION AND CONTROL MECHANISM Filed Jan. 10, 1945 Dec. 11, 1951 w. K. ANDREW ETAL 2 3 Sheets-Sheet 3 IIIIJI I. A wh m m il 1. T u r h MO:

mwmgmgs-m Mn nhu I MW Patented Dec. 11, 1951 U NI T E D' F1. S

According itO this inventioman.automatic millai" ing machine is:v arranged .sto 'efiecL-a- EOIltiIlllOHSil maticmilling: machines of -the typeadapted to succession zof.."series..'.ofi indexingzand: feedings; operatein a continuouslcyclea actions with respectitd a spluralityrofz workpieces A-general object ofthe invention is. toprovide: 5 For this purpose;-.the:mach=ine.t-is providedswith an .improved millingsmachine arranged :toefiect multiple: indexing fixture ateach'fen'd of the table successive series of. machining, operations auto-. the .control system:tbeing;so.-.Larranged.fthat each i; maticallyi fixture, in turn, is fedztriacuttengang repeatedl Another object of. theinvention is toprovidesa WithLinterveningvindeX-ing actionsmoefiecta serie milling machinexhaving aaxplura'lity of indexing of machining=..cuts on the workpieces; At thetendtn workholders; together...-with. .a control system: of ta series. of. minor acyclesmithi.respectifcoi one arrangedto efiectia series of feeding and indexing; fixture;z.vthe table: is. traversed -.::automatioa:lly:;- tin; movementswith.respectto: one. work ho1de'r,.fol'- bringzup' tha'otherifixture; which isasthenifed (to lowed automatically by a 'similanseriesiof feeding the; cutter; gang repeatedljsinthez same ananner tzi and. indexing. movementswith. respect to another. the .majon'cycle beingrirepeated continuously; A11 work holder; fluid pressure control system efiectsz-stheisucces -z Another objectofeth'e invention is" to provide-- an;:impro.ved-.actuatingzLand controlling mecha-' thezztransition.frmmminonicuttingistrokes td.:the nism for an. automatic milling machine, majontraversing strokebeing efie'cted by. retract? Another object. .is to. provide. antaautomatio ing-raniintermediate reversing'tripidogz; machine tool in which-a reciprocating-carriage Thezioregoingand:otlieriobjectsiof;thistinvenez is arranged tov operate. alternately through two tion, zwhich;willebecome :morev readily :discerniblen series of feedingand rapid traverse movements. from: the followingsdetailedrdescriptiomawhenxs Still another. object, of the invention is. to .proev read moon-junctionwithtthe accompanyin draw;-;-

This. :invention relates generally to -machine tools and more particularly to animproved auto vide-a fully automatic multiple work fixture for; ing:,. may.be achievedby meanszofz-the particular;

illustrative apparatus rthere shown :in :the; several view's ,'of:.whichi;

a machine tool.

Another objectis to provide an improved cone; trol. system for a" power 'actuatedmachinez tool- Figurel is .a general iview in frontselevationofz carriage arranged to-actuate:.the-'carriage auto-. asmillingmachine fitted awith apparatus embodye matically a lseriesfzof... strokes;:.of:. difiering,u ing the principlesof theapresentinventiongr. lengths. Fig.;2 is an enlarged fragmentary ppla-n view 'oit;

Another object is to provide animproved ma.-'- the cooperatingzworkzand'cuttersupporting strumchine tool .having: movement controlling .tripy. tures of: the machi'ne shown in';Fig'. .-1','withxpartsee mechanism so arranged that. selected tripping broken awayYto'1;-better disclose:rthemactuatingzg elements may be rendered inefiective during opera .mechanism 5 Y ation of the machine to vary the. characteristics:- w' S-a Schematic ram of the continuous ofthe operating cycle. reciprocating;.operatingeoycle ofytlie :machin'e;;;

Another object is. to provide amachine tool 1 -4i an.e ed"fragmentaryiview=in.-fronti with tripping mechanism including a trip dog elevation of thework supporting structureshownzr. arranged to be retracted selectively for .varyins 40 -l with-par sw yfind With-;the:-;- the tripping-action. cutters and triprmechanism shown :inwphantom;

Another object is to provide an improved Fig, 5 is -a-.view in verticals.transverserzsectionatrol system for ettecting automatic indexing,v through the w rki l inafim 1 clamping and LraVersing actionswin machine ture,:taken;on:the'planesrepresented byahexlin'esan tool. 55 in Figs;.l,-2 and-hand, 1.

A-further object is :to provide anautomatic Fig.. 6 is;:..a= .;fragmentarytviewoin:zhorizontalz; Workretaining.fixtureoperablydisposed to effect transverse section:.throughxtheqztable; anemone. positioning of a plurality ,of-workpieces and .alter--' theplane .representedaby theilinesaG- liin Figs. nateindexingandlocking of the workpieces dur- 1 4 an fi and showing the retractile trip d r ing a series of automatic cuttingoperations: 5 rier-.. thereon. The i particular": machine stool shown:v in \1 the- A still further object is. togprovide'sa multiple: drawingsasz. exemplifying-a:practical supporting workifixture. wherein a series of work retaining; structure fitted. awithl aapparatus' emloodying-*thie' spindles are automatically indexed by: action. of; i principles-0f thefipresent inventionis millin'g a sine-1 i in Plungen. 551 machine-10f:the-ebed type, generz'i'llyi similar' 'iri sive actionszirnresponse $0 tripping. mechanism; I

form to the machine disclosed and claimed in copending application, Serial No. 431,908, filed February 23, 1942, now Patent No. 2,407,913, dated September 17, 1946 with certain changes in the driving mechanism, the present machine being fitted with a separate motor for actuating the table. However, it is to be understood that apparatus embodying the invention may be utilized with any of various other machines.

Referring more specifically to the drawing, and particularly to Fig. 1, the milling machine there shown comprises essentially a hollow bed or base l that constitutes the supporting frame of the machine and forms a housing for much of the actuating mechanism. At the rear of the machine, the base lll supports an upstanding column structure ll fitted with a spindle carrying head I2, that is vertically adjustable by means of a hand wheel [3 at the top of the column. The spindle head 12 carries a horizontally disposed cutter driving spindle I4 mounted in a quill l5 that is longitudinally adjustable in the head by.

means of a hand wheel l6 projecting at the right side of the column, as is usual in milling machines of this type. The spindle I4 is fitted with a suitable gang of cutters 29 and is arranged to be driven by the usual motor (not shown) mounted in the bed [9 and electrically connected to be started or stopped by a push button controller 2| mounted on the left side of the column H.

In front of the column II, a work carrying table 25 is slidably mounted on the upper surface of the bed It for longitudinal reciprocating movement in the usual manner in cooperating relationship with the cutters 20. Power movement of the table is effected by a separate motor (not shown) mounted in the base [0 and electrically connected to be controlled by a push button controller 29 mounted on the column II adjacent to the controller 2|. Longitudinal movement of the table 25 by power from the motor may be caused to occur in either direction at either feed or rapid traverse rate through manual actuation of a controlling lever 21 on the front of the bed l0. Movement of the lever 21 to the right or to the left effects movement of the table in the corresponding direction. Tiltingmovement of the lever outward or away from the table provides for movement at rapid traverse rate while tilting of the lever inward or toward the table provides for movement at feed rate, the rate of feeding movement being established by selective adjustment of pickoif rate changing gearing mounted within the bed I0 and made accessible by opening a hinged door 28.

Control of the rate and direction of movement of'the table 25 may also be effected automatically in various cycles through the operation of trip mechanism fully described in the previously mentioned copending application and including a central unit constituted by a vertically movable rate changing tripping post 29 flanked on each side by reversing plungers 31 and 92, as shown in Figs. 2 and 6. The tripping post 29 is arranged in the usual manner to effect movement at rapid traverse rate when in its upper position and at feed rate when in its lower position.

The reversing trip plungers 3| and 32 are adapted to be engaged by reversing trip dogs mounted in the usual manner on the front edge of the table 25, such as the dogs 33 and 34, shown in Fig. 4, which serve to delimit the terminal positions and to effect reversal at the extreme end of travel of the table in either direction. As more fully explained in the previously mentioned patent, the reversing plungers operate, when depressed, to effect both reversal in direction of movement and change to rapid traverse rate of movement, whereby the table may be caused to return at rapid traverse rate after reversal. Ordinarily, the table is fitted with stop dogs arranged in conjunction with the reversing dogs and operative upon the tripping post 29 to stop the table in the event of failure of the automatic reversing mechanism. However, this safety feature has been omitted from the drawing to simplify the illustration.

As shown in Figs. 1, 2 and 4, the table 25 is provided at its opposite ends with opposed work holding indexing fixtures or heads 4| and 42 that cooperate with a central tailstock structure 43 to support a plurality of workpieces 44 at opposite sides of the cutter gang 29 for alternative engagement with the cutters.

In operating in accordance with this invention, one of the indexing heads is fed to the cutters 29 by a series of approaching and feeding strokes with intervening retracting and indexing movements for effecting the desired number of cutting actions upon the workpieces, there being a plurality of similar workpieces 44 in each fixture. At the completion of the cutting operations on one set of workpieces, the machine functions automatically to withdraw and unclamp the finished workpieces while advancing the other indexing head to effect a similar series of cutting operations upon the workpieces held by it.

The feeding and indexing of the workpieces occurs alternately in a series of strokes or minor cycles through the action of the automatic trip mechanism until the required number of milling cuts has been effected. The table 25 is then automatically reversed through a major stroke to withdraw the finished workpieces from the region of the cutter gang 29 and bring the new workpieces in the other fixture into cooperating relationship with the cutters. The new workpieces are then fed to the cutters, retracted, indexed, and then fed to the cutters again, the process being repeated as many times as necessary to complete the required number of cuts. In the meantime, the operator has removed the finished workpieces from the first fixture and replaced them with new pieces so that, after the last cut is taken, the table again traverses through its major stroke to complete a major cycle, the process being repeated continuously, as indicated diagrammatically in Fig. 3.

The particular workpiece 44, shown in the drawing is a thread cutting tap and the operation to be performed the milling of four longitudinal flutes in equally spaced relationship. As shown in Fig. 2, each fixture is arranged to receive eight taps, each tap being supported at its entering end by a center 45 carried by the tailstock unit 43. At their other or squared driving ends, the taps are engaged by suitable chucks 49 on the ends of work holding plungers or spindles 41, rotatably and slidably mounted in the headstocks Hand 42, as best shown in Figs. 2 and 4. Each plunger 41 is provided with a spring 48 that urges it into engagement with the associated tap 44, each tap being supported in alignment with its respective plunger and tailstock center by means of a V-block 49. For clamping the taps tightly between centers, each pair of plungers 41 has associated with it a fluid pressure cylinder 50 provided with a cooperating piston 5|, the piston being connected by a rod 52 with a cross head 59, which operates upon tan-wingers through A i terposdcempress1tn tlie'fdesired'lengthi" at"which-time the-lefttet springs 54. I minalreversingdog "ts-engages 'the-left=revers After the tapsh'ave'beenplaced irithe V-bldtaks' ing plun'gerfi l *thereby reversing'the directioni inloading the'fi'xture; fluid-pressure from" a," and' rate ofmovementofthetablefor efiecting source represented"by "an inlet pipe -565m ad-* ar'eturn"'strokeat rapid-traverse rate,-as pre--* mitted through a'clamping valve Wand-a mm viously explained:

nec'ting pipe 58 intdone end-of amanifoldf 59- Asthe table-movesto'thedeft, the-actuati ng formed in thebody of the fixture andconnected 7 am? "oi theclampingvalve El -moves ou't' of with each of thecylinders-tfl; the" t zressure*forc V engagemenvwiththe clamping dog "it; thereby ing the plungers l'l forward-into engagement m effecting-a"closure ofthe-valveanda'consequene with the taps. At the other end of the manifold releasefofthe clamping'action upon the work 59, there isa va'lve'member iill, which is -con=- holding-plungers-M: The 'indexingdog-JU-is of nected with the associated piston" 5l-' and ar-"-'-- thepivoted type-and-,-upon'movementto-thedeft ranged to open when the plungers; move to a withthe table 25' is-deflectedthrough its pivetal clamping position, thereby admitting pressure m action by" the *pins'll ofthe indeXing plate-12;

into aconduit 6|. As best'shown'irr-Fi'g':- 4 thewithoutimparting mot-ion -tothe'-plate. After; conduit 6| communicateswith a manifold-6'12- thefiridexingdog-TG clearsthe indexingplate 12, that connects with aseri'es'ofvertical cylinders thereturn -stroke of the table is terminated 63. Each cylinder 63 'is' located beneath fonethrough action of' acentrallylocatedintermedi pairof the plungers'i and'is provided with 'a" fi ate'reversing dog-l9, which-has associated with: pistonfi l carrying a clamping "shoe'fifi; thear it-a feed" dog sil that depresses the trip plunger rangement being such that, when-pressure is 29 to cause the table-to moveatfeedrate: as admitted to the manifoldES, the-pistons 64 are the reversing dog l -moves into engagement with forced upward to engage the clamping shoes withthe-reversing tripplunger 32. This -completes= a'wedg'ing action between the adjacent plungers g a minor-cycle and causes the table 25 to again: of each pair. 7 advance to the rightat rapid traverse rate to Although the fluid pressure system *could be eifectn second cutinth'e workpieces. actuated hydraulically, his in this instance; ar- A-s'the-table-advancesto-theright in a-second ranged to be operated pneumatically'by pres-- minor-'-stroke for the-second cut, the-indexing: su re,'such as is available in the usual shop air 5 dog"'l0-again-engagesone of the indexing. pins 1, line. H of" the indexing cam plate 12 to turn it 1 As best shown in FigIZ the two fixtures 4| and through a quarter tur n. As best shown in Fig. 5;- 42 and their cooperating'tailstock centerst5 are the-cam plate -12 is provided on its-inner surface arranged in staggered relationshinin such manwith a camtrack 82-; which cooperates -with--a-- nor that each workpiece is aligned with an inde igio'llower roller- 83 on an indexing rack bar' 84 pendent cutter 680i the cuttergang 20. By'this disposed transversely of the head 'beneath the arrangement, every other cutter'is-positioned to workholding'plungers M.- As appears in 'Flgsv2," cooperate with a workpiece in the fixture-4|, 4, and 5, each of the-plungers-M is'provlded with: while the intermediate cutters cooperate with gearteethconstitutinga relatively long-pinionworkpieces in the fixture 42. With" the tablein i-sfi' thath'as meshing and sliding engagement i the position shown in Figs. 2 and 4, the clamping with rack teeth on the indexing bar 84. valve 5? associated with the rightfixture' 42"is" As shown, the'cam surface82 presents aseries': closed, hence no pressure is exertedmpon the" of' lobes or dwells corresponding in number'to work retaining plungers; the plungers being inthe number of cuts'required in the workpiecesreleased condition for receiving workpieces." 5;- in' this instance, four; The rack bar 84 is biased With the left'fixture M loaded with work toward the -cam surface 82 by a spring inapieces 44 as indicated in Fig. 4, the'machine may" manner to hold the follower roller 83 against 2 be put into operation by starting 'thetable'in" thecam, the arrangement being such that as movement to the righ't'at rapid traverse rate the "cam is turned through each quarter turm, through the manual actuation of the control" 1b the-rack-'84"is moveda sufilcient distance to turn le'verzl outwardly and-rightwardly to causethe the workholding plungers: t! 'simultaneously le'fthand fixture M to approach the cutter gang through 90, thereby properly indexing all eight"- 2ll.' As the table moves to the right, an indexe of'thetaps- M for'sequentially machining the ing dog 18," mounted on the front of thei'b'edilfl," four i'equallyspaced' flutes. Immediately followengages one of four indexing pins 1! on an'im- 'ingthe indexing movement, the actuating arm dexing plate 12 rotataby mountedfon'the side 15 of the clamping valve 51 engages the clamping of the head M to effect rotation of the plate dog 14' toopen the valve and effect clamping of through approximately 90. Immediately fol the plungers'fl inthe indexed position. The feedlowing the indexing movement, a clamping dog dog." then engages the tripping post 29, as be- M'on the bed engages and pivots anactuatin'gjmj fore, to' change the rate of travel from rapid arm .5 of the clampingvalve 51 associatedwith traverse-rate to feed rate for cutting the secondthe head 4!, thereby actuating" the valve-and flute effecting rigid clamping of the workpieces 'in'the" The relative movements of the cutter andthe manner previously explained in connectioni'with workpieces in the twoheads are shown diagram the head 42, the mechanisms of thetwo heads m matically in Fig. 3, the lines representing the being substantially identical. strokes of travel constituting a full major cycle,

By the time the clamping action has occurred," with the horizontal dotted portions indicating the, workpieces 44 "will have been 'advanced 'al movement at rapid traverse rate and-the inclined most to the respective :cutters '68. Atthis-posi- I solid portions indicating movement at feed rate; tion; a feed dog" on'the front of the amaze--70- During the approach movement from thestart' engages the tripping post 29jand moves it dowm ing-"position; the cutter gang 20, which may be wardly'to the feed'rate'position, whereupon the represented by the cutter 68 indicated above'the'- table advances at feed rate. totfeed I the 1work= cycle diagram, and the left workpieces 44, shown pieces into the rotatingcutters 68. Thefeedingf' below" the diagram,- have relative approaching action continues until the first flutels"cut"to75movementat rapid 'traverse"raterasindicated by? 7 the horizontal dotted line 90, while the indexing and clamping operations are being effected. When the feed rate dog engages the tripping post, the relative movement continues in the same direction at feed rate, as indicated by the sloping full line 9|, to cut the first flute. Following reversal at the end of the first cutting stroke, the relative movement occurs at rapid traverse rate in the return stroke, as indicated by the horizontal dotted line 92, to complete a minor cycle. At the end of the return stroke, the movement occurs at feed rate for the short distance indicated by the inclined line 93, whereupon reversal occurs and relative movement to bring the cutter and work back into engaging position is effected, as before, at rapid traverse rate indicated by the horizontal dotted line 94.

Repetition of the minor cycle continues in this manner through as many feeding and return strokes as are necessary to effect the required number of cuts upon the workpieces, the number, in this instance, being four.

As the workpiece and cutter are caused to approach for the final cut of the series of minor cycles, the indexing dog I turns the indexing cam plate I2 to its final position, thereby moving the indexing bar 84 to its extreme inner position for indexing the workpieces for the last fiuti cut. coincidentally, a cam lobe 96 on the pe riphery of the cam disk 12 engages a follower roller 91 associated with a control valve 98, which functions to change the mode of operation of the tripping mechanism to cause it to effect a major stroke for withdrawing the finished.

workpieces in the left fixture 4I and advancing the workpieces held in the right fixture 42 toward the cutter gang 20. This is accomplished by retracting the central reversing dog I9 and its associated feed dogs from cooperating relationship with the tripping unit, whereby the rapid traverse return movement from the cutting of the final flute is permitted to continue as indicated by the horizontal dotted line I00 on the diagram in Fig. 3, through a full stroke of movement. When the table 25 moves to retract the fixture H and bring up the fixture 42, the actuating arm I5 of the clamping valve 51 on the fixture 4I moves out of engagement with the;

clamping dog 14, thereby unclamping the finished workpieces in the fixture M to release them for removal. As the table continues its movement, a dog mechanism I02 on the back of the table engages and actuates a reversing switch I03, which functions to reverse the spindle driving motor, thereby causing it to drive the cutter gang 20 in the proper direction for engaging the appropriately positioned cutters 68 with the workpieces 44 in the right hand fixture 42.

As best shown in Fig. 6, the retractile center or intermediate reversing dog I9 and its associated feed dogs are carried by a trip dog carrier I04, which is slidably mounted within a socket I05 disposed in the front face of the table 25. When.

the dog carrier I04 is in an operative position, it is fiush with the front edge of the table, thereby supporting its reversing and feed dogs in line with those secured directly to the table, as may be seen with reference to Fig. 4. To provide for shown, the trip dog carrier I04 has secured thereto a pair of spaced guide rods I06, each of which is fitted with a compression spring I0I arranged to bias the dog carrier I04 to its retracted position. As the traversing movement of the table 25 continues past the point at which the retracted central reversing dog 19 would otherwise operate, as indicated by the horizontal dotted line I00 in the diagram (Fig. 3), another indexing dog I00, generally similar to, but reversed from the dog I0, engages one of the pins II of the indexing plate I2 carried by the right fixture 42. This indexing plate corresponds to the plate I2 of the fixture 4| and, as rotated, effects an indexing movement of the workpieces in the fixture 42 in the manner previously explained in connection with the fixture 4|. As the plate I2 turns, it withdraws a cam lobe, similar to the cam lobe 96, from beneath the actuating plunger of a valve I I0, which is generally similar to the valve 98 of the fixture 4I. Thispermits the valve I I0 to open and admit fiuid pressure from the source 56 through a conduit III, the valve H0 and a conduit II2, which leads to the valve 98. In the valve 90, the conduit I I2 is permanently connected with a conduit II3 (Fig. 5), which leads from the valve to the rear of the table 25. As shown in Fig. 6, the conduit II3 connects with a cylinder II4 integrally formed in the rear edge of the table and fitted with a piston II5 having a rod II6 connected to the dog carrier I04. When the valve I I0 is opened upon rotation of the indexing cam plate, pressure is admitted through conduits H2 and H3 to the cylinder H4 and acts upon the piston II5 therein to move the dog carrier I04 forward into active position in opposition to the compression springs I01. With the dog carrier I04 in the operative or active position, the central reversing dog I0 is again in position to effect reversal in the minor cycle of table operation.

Further movement of the table to the left causes the clamping dog I4 adjacent to the right end of the machine to engage the actuating arm I5 of the valve 51, thereby opening the valve and admitting pressure to clamp the workpieces in the fixture 42. Following the clamping action, a feed dog III engages the control post 29, moving it downward to feed position for effecting the feedingaction for cutting the first flute. At the end of the first cut, the reverse dog 34 engages the reverse plunger 32, thereby causing reversal at rapid traverse rate, as indicated on the diagram (Fig. 3) by a horizontal dotted line I20 to complete the first minor cycle with respect to the right fixture 42.

Since the dog carrier I04 is now in the active position, a trip dog I2I on the carrier I04 engages the trip post 29 to shift it to the feed position as the intermediate reversing dog I9 moves into engagement with the reverse tripping post 3| at the end of the first minor cycle.

The table, in moving to the left in the next minor stroke, then effects the indexing, clamping and fiuting operations, as previously described, the minor cycles being repeated until all of the flutes are cut. Upon the last indexing movement, the cam lobe of the cam plate I2 closes the valve IIO, thus cutting off pressure to the cylinder H4 and permitting the springs IN to retract the dog carrier I04. Hence, when reversal occurs at the end of the last cutting stroke, the intermediate reversing dog I9 will pass the trip plunger unit and permit a full stroke movement of the table rightwardly to complete the 75 major cycle.

Since the valve 98passociatediwithithe leftifixture "4 l was: closedhbyi the? last indexing, movement of that fixture,- continuedmovementrof the table: .to thesi-rightiiin z-themajon stroke serveswto open the valve upon thefirst indexing movement 5 effected by the ileft'indexing :dog' 10 because the cam: lobe 96 will be turned out i from: :undenthe follower roller1-9 7. if Thusppneumatic pressure is admitted fromzithesourcefifil through the valve --98:.and .theconduit llastotheicylinder' M4 for repositioning the dog carrier I04 in active-position,.to :effect thesucceeding minor indexing cycles.

Although the particular apparatus shown is arranged for machining four flutes in each of the workpieces, it will-be readily-understood that the mechanism may beadapted-to efiectany required number of successive machining-actions by providing appropriately shaped cams and making various oth-eradjustments. Furthermore, the 1 control mechanism is shown: as being actuated z-pneumatically, butit ,isiobvious that -it may be -;.adapted for operation ,hydraulieally, .-mechani- .cally or electrically.

"From. the foregoing ..detai1edfdescription and 1 I r explanation of operation :ofzthe illustrated exemnplifying apparatus herein set forth as a practical :embodiment of the present invention, titwillappear that there hasbeen provided an improved machine tool actuating and control mechanism that is especially,adaptedzforgperforming automatically continuous cycles. of reciprocation of .a machine, member in anewand .improvedmanner.

Although theillustr'ative embodiment of the invention has been described in detail for the purpose of fully disclosing a practical structure incorporating the invention, it is to be understood that the particular apparatus herein set forth is intended to be illustrative only and that the novel characteristics of the invention may be incorporated in various other structural forms without departing from the spirit and scope of the invention, as defined in the following claims.

The principles of the invention having now been fully explained in connection with the foregoing description of the embodying apparatus, we hereby claim as our invention:

1. In a machine tool having a reciprocating table, power actuating and controlling mechanism for effecting automatic reciprocating movements of said table, a pair of reversing trip dogs carried by said table at positions defining terminal points in the path of movement of said table and arranged to operate upon said power actuating and controlling mechanism to efiect reciprocation of said table between said terminal points, another reversing trip dog movably mounted on said reciprocating table at a position interposed between said terminal trip dogs and operative when moved to active position to effect a shorter reciprocating movement of said table, and means operative while said table is in motion to move said interposed reversing dog to inactive position selectively, whereby the length of the stroke of movement of said table may be changed during operation of the machine.

2. In a milling machine, a base, a power actuated movable work supporting table mounted on said base, trip mechanism mounted on said base and operative to control power movements of said table including movable trip means for actuating said mechanism,-a plurality of trip dogs carried by said table in the path of said trip means to engage and move said trip means for actuating said mechanism, and power operated 10 meansmarriedz-by. said; tablerand: arranged. to re- -tract oneof-said dogs selectively from cooperatingposition, wherebythecontrolling effect of said a=trip; mechanism: andcooperatingdogs may be varied while said :machine is in operation.

"3; [n a: millingmachine having a base and a power actuated work supporting table movably mountedron said; base, trip mechanism mounted on said base and operative to control power movements .ofisaid tablev in a-variablereciprocal .pperatingcyde including movable :trip means for ;.-ac.tuating.said-mechanism, a trip dog movably mountedon: said table ina-manner to engage and r, actuate saidtriptmechanism; and power? actuated -means carried said-tableand arranged to move -said,dogi into ;or outof cooperating relationship --,withsaid.trip mechanism selectively.

-. 4., Inavmilling machine having a, power actu- .,ated -,Wor,k supporting table, a. plurality of trip .dogs; carried ;by said table -for movement thereiwithin a pathrof tripping action,;tripping mecha- :ifismarrangedtobe. actuated by said dogs in moving along said path andoperative .to control power. movements .of said-table, a retractile trip dog carried ,by, said table,.- and fluidpressure 'op- Y aerated, mechanism. carried by said table :and connectedto. actuate.saidretractiletripdog for moving. it....into. orout of said path .of trippingaction vs electively.

5. Insarmachine tool havingia baseand a power actuatedcarriage:movably mountedon said base, .,tripping; mechanisnnmounted on saidbase, and ,operativeqto control, power, zmovementsaofwsaid carriage including movable trip means for actuating said mechanism, a retractile trip dog mounted on said carriage in the path of said trip means in a manner to engage and actuate said trip mechanism, and power actuating means mounted on said carriage and arranged to move said trip dog into or out of position in cooperating with said tripping means.

6. In a machine tool having a power actuated carriage, tripping mechanism operative to control power movements of said carriage, a retractile trip dog mounted on said carriage, and fluid pressure actuated means mounted on said carriage and arranged to position said trip dog into or out of cooperating relationship with said tripping mechanism selectively.

7. In a milling machine, a frame, a milling cutter rotatably mounted in said frame, a work supporting table movably mounted on said frame in cooperating relationship with said cutter, a source of power operatively connected to move said table in either direction selectively, a pair of reversing trip dogs fixed in spaced relationship on said table, tripping mechanism including a tripping unit extending from said frame between said trip dogs and operative upon engagement by either of said dogs to effect reversal in the direction of movement of said table, a movably mounted reversing trip dog carried by said table between said spaced trip dogs and likewise operative upon engagement with said tripping unit to effect reversal, and selectively operative means actuated by movement of said table to move said movably mounted trip dog out of cooperative relationship with said tripping unit, whereby said table may be caused to reciprocate through a stroke delimited by said fixed trip dogs or through either of two shorter strokes delimited by said movable trip dog and one or the other of said fixed trip dogs, depending upon the position of said movabletrip dog relative to said tripping unit.

8. In a milling machine, a frame, a cutter rotatably supported by said frame, a work supporting table slidably mounted on said frame in cooperating relationship with said cutter, power operated means arranged to effect reciprocating movement of said table, trip mechanism operative to control movement of said table, a pair of reversing trip dogs mounted in spaced relationship upon said table and operative upon said trip mechanism in manner to effect reversal of movement of said table at predetermined terminal positions, another reversing trip dog movably mounted on said table between said first-mentioned trip dogs and arranged to cooperate therewith for, effecting reversal of movement of said table to provide for reciprocation thereof in either of two cycles of movement, and means to move said intermediate trip dog out of cooperating relationship with said trip mechanism to permil: movement of said table from the one to the other terminal position, whereby it may be caused to operate in either of said two cycles of movement selectively 9. In a machine tool, a frame, a carriage movably mounted on said frame, power actuated mechanism in said frame operatively connected to drive said carriage, control mechanism in said frame arranged to control said power actuated carriage driving mechanism, trip dogs adjustably mounted on said carriage, tripping mechanism on said frame arranged to be actuated by said trip dogs during movement of said carriage and operative to actuate said control mechanism, a

12 dog supporting element movably mounted on said carriage, trip dogs adjustably mounted on said movably mounted dog supporting element, and control means arranged to move said dog supporting element on said carriage to position the dogs thereon in actuating or non-actuating positions selectively relative to said tripping mechanism, whereby the cycle of operations eflected by said trip dogs may be varied through control of the position of said movable dog supporting element.

WILLIAM K. ANDREW.

RICHARD H. FORD.

EDMUND W. JUST.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,866,348 Ferris July 5, 1932 1,938,770 Archea Dec. 12, 1933 2,121,923 Neubert June 28, 1938 2,155,864 Krause Apr. 25, 1939 2,169,484 Armitage Aug. 15, 1939 2,190,858 Bennett Feb. 20, 1940 2,261,052 Coflin et a1. Oct. 28, 1941 2,350,975 Rodder et a1. June 6, 1944 FOREIGN PATENTS Number Country Date 118,971 Great Britain Sept. 19, 1918 

